A Doctor Who movie is in the works, but not clear if David Tennant will star

A feature film based on BBC's hit sci-fi series Doctor Who is in the works, according to the BBC.

A spokeswoman for BBC Films confirmed that "a script is in development," the BBC reported in a story about David Tennant's upcoming guest appearance as the Time Lord in the Doctor Who spinoff series The Sarah Jane Adventures.

BBC entertainment correspondent Lizo Mzimba said there were no guarantees a film would be made; if the project went into full production, a release would be a long time coming. It's also unclear whether Tennant or another actor would fill the title role.

In the meantime, Tennant, 38, will appear over two episodes of a new 12-part Sarah Jane show, which starts in September, the BBC reported.

Russell T. Davies, executive producer of The Sarah Jane Adventures and Doctor Who, said it would be a "full-on appearance" and "not just a cameo."

In the mothership series, Tennant is being replaced by Matt Smith, 26, who will appear as the 11th Doctor next year.

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